Motor-driven hand tool



Jul 25, 1944.

w. M. EM ERY MOTOR DRIVEN HAND TOOL Filed Nov 25, 1942 2 Sheets-Sheet 1'Fl G. l

FIG-.2.

VENTOR.

July 2 w. M. EMERY I 2,354,307

MOTOR DRIVEN HAND TOOL Filed Nov. 25, 1942 2 Sheets-Sheet 2 PatentedJuly 25, 194 4 William M. Emer Shaker Heights, Ohio, assignor to TheRotor Tool Company, a corporation of Ohio . Application November23,1942." Serial N o. 46(i,60 1

. My invention refers to improvements in power driven handtools withspecial attention to grinders, nut setters, drills,'.and' the like wherethe tools are of such horsepower that they develop substantial reactivetorque which must be resisted by the operator. This includes such toolsthat for'efficient. or convenient operation and :usually for support,the handle is'positioned substantially axially or parallel thereto."I'hisinvention bears some similarity infield and objects to thatcovered in my Patent many classes of applications,.-has certainlimitations which are overcome in my present inven-, "tion, principallyby avoiding clo'se indexing between the forearm of the operator and thewheel guard and allowing for varying-the angle between 'th guard and thework by the flexing of-the wrist.

With grinders, a limit has been found above 'which in the past ithas'been ineflicient to increase the horsepower and the torque becauseof the inability of'the operator to resist the reactive torque bygripping the straight or axial handles without excessive fatigue.Infact, the

majority of the fatigue in the-use of suchtools is'directlytra'ceable'to finger, hand and wrist fatigue, so much so that incontinuous operation theoperator seldom presses sufliciently upon the.

workto'utilize the full horsepower capacity of the tool or to securemaximum removal from the work'being ground. The work accomplished isfurther reduced by necessary rest periods.

Furthermore, if the wheel grabs'while grinding the inside'radius of ahole the operator is often unable to hold the tool and frequentlysuffers injury. 7 Y

Some years ago spade handles were used on such tools. A spade handleconsists ofa handle like that of a'spade. It has a hand contactingportion substantially perpendicular to and across last five yearswhichsuch' ha'ndles have been used with large'tools, no method hasbeenadvancedby any other that successfully overcomes the fatigueproblem'thatso limits .the produotionand horsepowertorque capacity of this v typetool. My'previous il' ivjerition bylo'nger le- #2,301,264, to whichreference will be made. My previous invention, although very helpfulwith verage places'the reactive torque largely midway on'the forearmo'f'the operator. In my present invention the reactive "torque'i's'applied through .my torque arrestor lever to the lowest point of theforearm namely the. bony structures of the forearm which in partconstitutes the'w'rist j oint'and the heel of the hand adjacentthereto,although 'I do not so limitthe sphereof' my invention. Morespecifically, the 're'activ'e torque 'presses'my torque arrestor leveragainst thehypothenar emithe handle'is normally-grasped; Theconventional straight handles when'normally grasped cross the palm ofthe hand distal (that is away from relative to the-body) to'both thethenar (that is the thumb) eminence and the hypoth- 'enar eminence. Thusmy torque @arrestor' lever substantially'doubles the lever-arm ascompared .to. conventional axial handles resisting the re- "activetorque. "Thisw'ould of course reduce the friction grip requiredto'hold'thehandle-50%, if

5* the handle were substantially round. r

My invention'goesstill further try-providing an irregular shapewhich'willhot turn easily in the hand, so thatthe hand need gn'o't begripped so tightly and the blood maycirculate'freely through thefingers. Also much of the wriststrain'and '1 fatigue is eliminated,because-theleverage-at the wristis reduced-to-a minimum by applying thepressure from the reactive torque to the'hypoth enar eminence adjacentto the wrist. There is no muscular-pad more-adequateand adjacent to thewristfto receive this reactive torque thrust, 1.40

the axis of the tool and-connected to the tool by rigid bales integral'to each" end of the handle.

"They have been largely abandoned after many T hands, especially thumbs,were injured when the wheel grabbed. The spade handle providedinsufiicient leverage to resist the stalling 'load 'of the motor andwhen this occurred the operator was often 'unable 'to disengage his handbefore injury."

T The so-called straight of axial "handles shown in my Patent 2,301,264are'the standard'conventional handles used today andtheiraxial position"is'more convenient for most. grinding, but in the" and moreparticularly the -"thumb and fingers.

I It is a known that that thel'ei's a defi nitel'imit t0 the size of theperiphery or diameter ofa bar which can be comfortably andtightlygrippedby a normal hand,'and.:such limitedlcircumference I does notallow-sufficient-leverage to resist the reactive torque in many cases, adiameter in the neighborhoodpf'. 1% incheshas been g'enerally recognizedin this fieldas a comfortable handle .omitted.

Fig. 3 isanend view of Fig. 1 substantially as tindicated by line 33 ofFig. 1.

Fig. 4 is .view from the other end i substantiallyas indicated by line44 of Fig. 1, held in the-left hand.

size. I have found that a range of one to two and one-quarter inches ispossible, although the extreme sizes are much more fatiguing wherereactive torque must be resisted.

Another object is to provide an abutment or lever arm projecting from ahitherto practically unused and ungripped portion of the handles of theclass of toolsalready described, said lever arm contacting the,.proximal end or portion of hypothenar eminence of the operators handadjacent to the wrist in a manner to form such a steep cam relationshipas to effect not more tha a minor resultant tending to open the hand orto act against the muscles maintaining the grip thereon.

Another object is to relieve the fingers, hand and the wrist of theoperator. from much of the fatigue incident to resisting the torquereaction of the motor by applying said forces more direct-' ly to thewrist and more adjacent to the forearm and tea muscular moundmoreadapted to receive themwithou't fatigue or discomfort.

Another object is to increase-the hourly pro- Jduction of theoperator'by reducing his 'or her fatigue and also by utilization of themaximum horsepower capacity of .the tool and. by the increase in thehorsepower capacity and also by .Also to provide. a, ,torquearrestor.lever, as I jwill hereinafter call an embodiment of myinvention'thatwill'innocase hamper the-.release of .the toolby the operator in thecase of an emergency.

' Other objects are-to increase the productivity .and metal removingcapacityl oi. portable tools without increasingbperator .labor and toreduce the labor .Of-g handling-. many. portable tools, so ,that warworkers such.-asuwomen, who have not suflicient hand-strengthto handlemany tools now on themarket; can takeover more types of this work. IFurther objects and novel-features of my construction willbepapparentfrom the following specifications and :claims when consideredto- .-.gether with theaccompanying-drawings in which:

V ,Fig. -1 is aside elevation ofv a conventional elecztric grinding tooltowhichhas been added embodiments oimy. invention. The wheel end han dleis grasped-with the left hand'and the other handle with the right. I

Fig. 2 is atop elevation ofFig. lzwith the hands of Fig. 1

Fig.6 is a top or plan'view of a spindle end Ill) ings or to thespecific type of motorization or tool selected for illustrativepurposes.

In Fig. l I show, as an example, the wheel end or work spindle handle Hof a portable grinder powered by a 180 cycle induction electric motormounted in a frame or housing I2 of approximately 2 horsepower underaverage working conditions but having a stalling torque. equivalent todouble the working torque. The speed of the grind wheel 9 is geared downto 4000 R. P. M. which at a 2 horsepower load results in a torque ofapproximately 31.5 inch pounds to be resisted by the operator bygripping two handles such as a wheel end handle H or live end handle 20which has a diameter of approximately 1% inches and is positionedsubstantially parallel to the axis of the motor in housing l2.

This means that while working at full capacity the operator mustconstantly resist 42 pounds torque at the surface of the grippinghandles. In an effort to preventthe' tool 'from'turmfng in his hand, hemust oftenwg'ripit so:.tightly-:that the circulation of blood tor-hisfingers is -so "-restricted'a's to further exaggerate his fatigue.

Under :stalling conditions, because the JnOtOl is a substantiallyconstant speed induction-motor, the stalling reactive'torque. initheexample:set forth would be about 63. inch pounds or-84pounds on thesurfaceof the handle to be resisted bygthe grip of the operator. If :thewheel grabs, the. tool is often wrenched' from the operatorshands;suddenly and without warningand he cannot contact the push buttonswitch. III to stop the-motor while the'tool is revolving. Fearthat thestallingv thing applies proportionately to s-mallen-tools" and it isobvious that in all events it ;will be possible for such'an operatorgto.usea tool-equipped with mydnvention possessing at-least twice thepoweri of the ,;maximum size"- tool=which she could use without the benefitof my.-.invention, becauseas previously;saidrmy invention more thandoubles the lever-arm. Also with a;.subs.tantially .round axial handlesuch as: is conventionally used-.the grip is-largely a-matter offriction whereas .with

w my utorque arrestor lever a positive abutment 'tweenthe axis of thehandle-and -the,axis-of the -wrist joint. By abutting mylever more. adjacent tothe wrist I -materially -.reduce this distance with theq-gearhousing 1,6. lever I 5' oifersa surface to .contactywith theproxi- :andreduce accordingly. the strain on' the muscles controlling the wristmovement.v v

The forward torquearrestor; lever 15 :arises from-the midportion-ofthewheelend handle as seen in l,sloping;,up; as shown toblend -.Theytorquearrestor "mal, endnor portion of;-hypothenar eminence: ,of

the hand ,ofmthe 'operatorfiubstantially normal to the tangent of thecylindrical surface-ofg-the handle I l10r'it can be described ashavingasteep cam: relationship with theihand. of the; operator .whicheffects only; a minor; resultant: of forces the torque arrestor abutmentI 5'or'2 I the case 'maybe, andif the direction of rotation-was re- InFig.2 it will be seen that-it i's 'set' at an angle of'about 2 to theaxis'of the handles so that it can besaid-that it is-set at a helixangle-on the handle'or work spindle I3 {of the tool which passes-throughhandle- I I. Whenlooking at the lever- I is'set at a right handhelixangle. If

the wheel (or work spindle I3) turned counterclockwise then the helixangle'of' thetorque arrester could be left'hand such as 'I'IFig. 5. on areversible tool," then both-angles would be used so that the combinationof both helix angles combining would create a wedge torque arrestorlever I5 and II with its apex pointed toward the grind wheeler-metalcutting end as viewed from the top as in Fig. 5. This construction isincluded in my invention.

Fig. 3 shows the torque arrestor lever I5 pressing against thehypothenar eminence of the operators left hand and approximatelyadjacent to the wrist joint of the forearm sometimes popularly calledthe heel of the hand. When the wheel as shown in Fig. 3 turns clockwisethe reactive torque tends to turn the handle I I counterclockwise to dothis, so that the torque arrestor lever I5 prevents the handle II fromturning in the hand of the operator even though his grip is materiallyrelaxed compared with the necessary required tightness if the torquearrestor abutment I5 were absent.

Fig. 1 also shows that the circumference or perimeter of the partactually gripped is not increased but additional leverage is provided bythe torque arrestor abutment pressing against the hand heel or wristjoint without making the size of the gripped part uncomfortably large.Figs. 1, 3 and 4 also show that in gripping any conventional handle ofreasonable and comfortable size that there is a normally unused portionof the periphery beyond the ends of the third and little fingers. Fromthis normally unused and uncontacted portion of the handle I project mytorque arrestor levers I 5 and 2|.

Such tools as grinders are used by some operators holding the wheel endhandle in the left hand as shown in Fig. l and other operators hold thewheel end handle with the right hand. Since the direction of revolutionof the wheel 9 is uniform it is obvious that in the latter case thetorque arrestor lever I5 will tend to turn away from the heel of theright hand if so held and accordingly in this case would not provide asmuch benefit in holding the tool in this way as when handle II is heldin the left hand.

To provide the maximum benefits of my invention under conditions wherethe hands are reversed left and right from the way shown in Fig. 1, Ihave also applied my invention in the form of a second torque arrestorlever 2| to the rear or live handle 20 in a modified form, as will beseen in Figs. 1, 2 and 4.

When grinding with a tool having the conventional right hand directionof rotation which is held with the right hand gripping handle I I andthe left hand gripping handle 20, then the torque arrestor lever 2| willbe pressed by the reactive torque of the motor against the heel orhypothenar eminence of the left hand adjacent to the wrist joint.

It will be noted from this explanation that when the wheel is rotated ina clockwise direction as shown in Fig. 3 then the left hand resistsversed then the right'hand resi'ststhe torque arrestor abutment or2I,-"=re gardless of which hands hold the handles I I- and-20, so longasthe thumbs of both hands are-toward the wheel or work spindle as theycustomarily are.

It will be seen that in the drawings that the switch I 0 is alwaysconveniently located for 'actuation by the thumb or first finger and Ihave 'invented means to-greatly assist the resistance of torque reactionin a portable" tool without I any encircling or other meahswhich mightcatch or strike the fingers, hands, or'body of the careless operator orwhich might interfere with the s11d den release of the tool-by anoperator in event of anaccident. I I l *In 'this-application whereIrefer to the grind wheel it should be understood that I mean anyabrasive polishing, metal cutting or working tool or other type workspindle.

It also should be understood that it is in the realm of my invention tomake either or both torque arrestor lever I5 and 2I either as anintegral part of handles II or 20 respectively or as a separate andremovable attachment thereto or with one of them integral with itshandle and the other detachable and/or adjustable angularly relative oneto the other.

The wheel guard 22 is clamped by bolts 23 to the wheel end handle II sothat it can be set on the handle at any convenient angle about the toolaxis relative to the torque arrestor lever I5. As seen in Fig.1 thewheel guard does not completely cover the wheel 9.

Bolts 26 have a common bolt circle radius likewise bolts 21 so that thewheel end handle with torque arrestor abutments I5 can be set at variousangles to handle 20 with torque arrestor abutment 2 I. Other means toaccomplish this indexing of the guard 22 and handles II and 20 are wellknown in the art and may be substituted without departing from thespirit of my invention such as attaching torque arrestor abutment 2|through association with the thread nipple 25.

Accordingly I claim:

1. A manually portable unit including the combination of a motor, ashaft rotatably driven thereby, a rotary work device attached to saidshaft, a handle having a substantially longitudinal axis positionedsufficiently adjacent to the line of the axis of said shaft andsufficiently parallel thereto to cause said handle to be turnedprincipally about its said longitudinal axis by reactive torque incidentto the motora-cting to revolve the work device, and a leverpredominatingly projecting from only one side of a portion of saidhandle and adapted to be pressed by said reactive torque against theproximal portion of the hypothenar eminence of a hand grasping saidhandle and to thereby resist the turning of said handle and tool unit insaid grasped hand under said reactive torque primarily by abutment withsaid proximal portion of the hypothenar eminence of said hand incontra-distinction to friction therewith.

2. In a manually portable unit including the combination of a motor, ashaft rotably driven thereby, a rotary work device attached to saidshaft, a handle having a substantially longitudinal axis positionedsufficiently adjacent to the line of the axis of said shaft andsufficiently parallel thereto to cause said handle to be turnedprincipally about its said longitudinal axis by reactive torque incidentto the motor acting to unit under said reactive torque primarily by:abutment with :said portion of thehyDQthenar .-eminenc e of said handin contra-distinction to iriction therewith.

3. Amanually portable unit including-,theicom- ,bination of a motor, ashaft rotably driven thereby, a rotary work device attached to :said

U'Shaft, a handle-having a substantially longitudinal axis positionedsufiiciently adjacent to the .line of the axis of said shaft andsufiiciently parallel thereto to cause said handle to he turnedifprincipally about its said longitudinal axis; by re- {active torqueincident t 0: the motor vacting-to re- -;volve the work device, a leverpredominating'ly projecting from one side of a ,portion Qf'SMd handleand adapted to 'be;pressed bysaid reactive torque :against theproximalportion of the hy- DOthBnaIzCIniIlBIiCi-Z of ahandgrasping saidhandleand-tothereby resistithe turning of saidhandleand1tool unit underaid reactive torque ,primarily by abutment .with said zproximal portionof the hypothenar eminence of said hand in contra-distinction tofriction therewith, said point of abutment of said lever with said .handbeing-nearer the wrist and further fromthe .axis def saidhandle therebyincreasing'the leverage of the handon the .tool and reducing,theleverage of the tool on the hand.

WILLIAM M. EMERY.

